The use of images for recording events is well known. Images can be captured using image capture devices such as a film camera, video digital camera, or a digital camera which captures digital images. Journalists use digital cameras such as the Kodak DCS 315 to capture images of newsworthy events. Digital cameras such as the Kodak DCS 330 are used to capture images at construction sites or other places where a visual record of the event is needed. Typically, a user of a digital camera captures a plurality of digital images which are stored on a removable memory card. These digital images may be transferred from the memory card and stored, for example, on a hard drive of a computer, recordable compact disc (CD), or other non-volatile memory associated with the user's computer. While digital images captured using a digital cameras are convenient to capture and transfer, the digital image are also relatively easy to modify, and the modifications can be difficult to detect. Accordingly, the authenticity of the digital image may be at issue.
Several approaches have been taken to insure the authenticity of a digital image. One approach is to connect a digital camera to a secure image storage facility over a secure link. Using this approach, the veracity of the digital image captured using the digital camera is dependent on the security of the link and the storage facility. While this approach may be suitable for its intended purpose, this approach mandates maintenance of a large image database and secure links to it. For example, WO 00/01138 (Steinberg) discloses an “escrow” security transmission wherein images “first data” are sent to a first location and other information “second data” is sent to a second location.
Methods of encoding data within a digital image are known to those skilled in the art. The encoded data can be used in an attempt to provide a “stamp of authenticity” for an image. However, if a portion of the image is modified, the encoded data may still remain intact, and the tampering will not be recognized. For example, U.S. Pat. No. 5,862,218 (Steinberg) discloses a camera using indicium received from a host computer to mark an image in a non-destructive manner to form a modified image data and add the indicium to an image header.
Encryption might be employed to verify the authenticity of a digital image. If an image is encrypted by the digital camera, it can be decrypted at a later time only by those with the proper decryption “key”. However, the utility of the image is lost for all those who do not have the decryption key. For example, U.S. Pat. No. 5,862,217 (Steinberg) discloses a digital camera providing encryption of an image during the acquisition process to attempt to avoid the existence of unencrypted image data.
Accordingly, while these methods may have achieved certain degrees of success for their particular application, a need continues to exist for a method for verifying the authenticity of a digital image which overcomes the problems of the existing methods. In particular, a need continues to exist for a method for verifying the authenticity of a digital image without reducing the utility of the digital image. That is, the method should allow use of the digital image by numerous users, of which only a portion may have a need to authenticate the image.